In recent years, there has been increase in the importance of computer-aided diagnosis (CAD) for supporting diagnosis by a doctor with the image analysis techniques using a computer. The most general function of the CAD is detection of a lesion site in an image.
When detecting a lesion using a computer, an examination image and a normal image are compared to find a difference. Calculation of a difference between two data items is a fundamental function in computer processing, and the computer processing excels at diagnostic imaging which detects a lesion site by comparing an examination image and a normal image which is a medical image of a normal structure.
However, position adjustment of the normal image and the examination image needs to be carried out for performing the difference calculation. Patent Literature (PTL) 1 discloses a method with which a landmark is set to each of the normal image and the examination image, position adjustment is carried out for the normal image and the examination image so as to match the landmarks, and a lesion site is detected based on the difference between the normal image and the examination image, thereby supporting diagnostic imaging.